There are many instances in which it is desirable to apply chemicals to range and pasture land. These chemicals may be in either wet or dry form. The purpose of the chemicals may be to fertilize the soil, treat insect infestations, treat weed infestations, or for some other purpose, such as killing all vegetation in preparation for cultivating and reseeding.
For example, infestations of weeds and woody vegetation regrowth in rangeland rob the soil of moisture and consume nutrients required by more desirable feed grasses. It is, therefore, generally considered to be advisable to control weeds and woody vegetation regrowth with a program of chemical spraying. With large tracts of rangeland, this chemical spraying can be accomplished effectively of aerial spraying using aircraft. For a variety of reasons it is often not viable to use aerial spraying with small rangeland plots. Cost is always a factor, as aerial spraying tends to be relatively expensive. Aerial access is often a factor, as the presence of natural or man-made obstacles in the vicinity of the small rangeland plot may prevent an aircraft from making a low level approach. Environmental concerns are sometimes a factor, as the rangeland may be positioned adjacent to bodies of water which could become contaminated through aerial spraying. Population concentrations are sometimes a factor, as acreage residences have extended out into rangeland areas as a result of urban sprawl. A further limitation is wind conditions. Chemical applicators which travel along the ground can work in a broader range of wind conditions due to the fact that the spray is released closer to the target surface then in aerial applications. There is, therefore, a need for an all terrain vehicle chemical applicator unit which can travel over rugged rangeland.
There are all terrain vehicles which are used on rangeland for other agricultural applications. An example of such an all terrain vehicle is Application PCT/GB90/01090 filed under the provisions of the Patent Cooperation Treaty and published as WO 91/01241 (Auty 1991). What sets a chemical applicator application apart from other agricultural applications is the effect that movement can have on spray dispersal patterns. With boom sprayers, 60 to 100 foot booms extend 30 to 50 feet from each side of the all terrain vehicle. Any change of direction, when transmitted the length of a 60 to 100 foot boom results in a destructive whipping action that damages the boom and disrupts dispersal patterns. With boomless sprays, spray nozzles must eject droplets over a distance. Any disruption in the “plane of ejection” causes droplets to either leave gaps, or collide in mid-air. Colliding droplets do not maintain their original size. This results in spray becoming uneven. Droplets which become too large after colliding, tend to bead and run off the plants leaves. Droplets which become too small after colliding, tend to hang in the air leading to off-target chemical drift.